Add missing lines-covered and lines-valid attributes (#17738)

This PR resolves an issue where the Cobertura XML report generated by
MyPy was missing the lines-covered and lines-valid attributes in the
<coverage> element.

Changes made:

- Added the lines-covered and lines-valid attributes to the <coverage>
element in the Cobertura XML report.
- Updated the CoberturaReportSuite test suite to validate that these
attributes are correctly included in the generated XML.

Fixes #17689

mypy/report.py

@@ -689,6 +689,8 @@ def on_finish(self) -> None:
             self.root_package.covered_lines, self.root_package.total_lines
         )
         self.root.attrib["branch-rate"] = "0"
+        self.root.attrib["lines-covered"] = str(self.root_package.covered_lines)
+        self.root.attrib["lines-valid"] = str(self.root_package.total_lines)
         sources = etree.SubElement(self.root, "sources")
         source_element = etree.SubElement(sources, "source")
         source_element.text = os.getcwd()

test-data/unit/reports.test

@@ -27,7 +27,7 @@ def bar() -> str:
 def untyped_function():
   return 42
 [outfile build/cobertura.xml]
-<coverage timestamp="$TIMESTAMP" version="$VERSION" line-rate="0.7500" branch-rate="0">
+<coverage timestamp="$TIMESTAMP" version="$VERSION" line-rate="0.7500" branch-rate="0" lines-covered="6" lines-valid="8">
   <sources>
     <source>$PWD</source>
   </sources>
@@ -81,7 +81,7 @@ def foo(a: int) -> MyDict:
     return {"a": a}
 md: MyDict = MyDict(**foo(42))
 [outfile build/cobertura.xml]
-<coverage timestamp="$TIMESTAMP" version="$VERSION" line-rate="1.0000" branch-rate="0">
+<coverage timestamp="$TIMESTAMP" version="$VERSION" line-rate="1.0000" branch-rate="0" lines-covered="6" lines-valid="6">
   <sources>
     <source>$PWD</source>
   </sources>